Introduction to Amines

Contributed by:

Jonathan James Mon, Jan 17, 2022 06:59 PM UTC

The highlights are:
1. Nitrogen Chemistry
2. Structure and classification of amines
3. Nomenclature
4. Properties of amines
5. Preparation of amines

2. Nitrogen Chemistry
 Nitrogen
will readily form 3 covalent
bonds (each atom already has 5 v.e-)
– Carbon forms 4 covalent bonds
– Oxygen forms 2 covalent bonds

3. Structure & Classification of
Amines
 Amines are derivatives of ammonia (NH3)
 Functional group = NHx
 Aromatic amines = aniline -->

4. Amine Nomenclature
 IUPAC (longest chain = alkane)  Common
– Primary – Primary
 Alkanamine  Alkylamine
– # is used to ID location of fcn’l group on
alkane chain – Secondary
– Can have diamines, etc.
 Alkylalkylamine
– Secondary
 N-alkylalkanamine
– Tertiary
– Tertiary
 Alkylalkylalkylamine
 N-alkyl-N-alkylalkanamine
– Multifunctional groups  Isomers
 Amine = substituent (amino), – Skeletal (C atoms)
– Carboxylic acid
– Aldehyde – Positional (NHx group)
– Ketone
– Alcohol
– Amine

5. Physical Properties of Amines
 State: low MW = gases @ RT
– Smell like ammonia
– high MW = liquids @ RT
– Bad odors
 BP: alkanes – Hydrogen bonding
 Water solubility
– Low MW = v. soluble
– High MW = soluble

6. Amines are weak Bases
 NH3 + HOH <==> NH4+ + OH-
ammonium ion
 CH3-NH2 + HOH <==> CH3-NH3+ + OH-
methylamine methylammonium ion
methanamine
 Amine Salts
– Acid + amine --> Amine salt + water (protonation)
 HCl + CH3-NH2 --> CH3-NH3+Cl-
methylammonium chloride
– Amine salt + base --> amine + salt + water (deprotonation)
 CH -NH3+Cl- + NaOH --> CH3-NH2 + NaCl + HOH
3

7. Preparation of Amines
 Alkylation in the presence of a base
– Ammonia + alkyl halide --> 1˚ amine
 NH3 + CH3Cl --> CH3NH3+Cl- + NaOH --> CH3NH2 + NaCl + HOH
 The primary amine will continue to react unless it is removed as it is produced.
– 1˚ amine + alkyl halide --> 2˚ amine
– 2˚ amine + alkyl halide --> 3˚ amine
– 3˚ amine + alkyl halide --> quaternary ammonium salt
– Quaternary ammonium salts may be biochemically
important
 Ex.: choline (growth reg.) & acetylcholine (nerve
impulse transmission)

8. Heterocyclic Amines
Nitrogen atoms are part of a ring system
Hemoglobin
-pyrrole derivative
Nicotine Caffeine
- pyridine derivative -purine derivative

9. Biochemically Important Amines
 Neurotransmitters
– Acetylcholine, norepinephrine
– Dopamine, serotonin
 Epinephrine
– Adrenaline
– Amphetamines - structurally related to adrenalin
 Histamine
– Responsible for effects of hay fever & pollen allergies
– These effects are counteracted by antihistamines

10. Alkaloids - plant based amines
 Nicotine, caffeine, cocaine
 Chocolate Theobromine - Greek (“theo” - god; “brosis” - food)
 Quinine, atropine The alkaloid atropine
is obtained from the
belladonna plant.
 Opium
– Codeine, Morphine (heroin)
Poppy

11. What do you need to know?
– Structural characteristics (know the functional group)
 Carboxylic Acids
 Esters
 Phosphate Esters
 Amides
 Amines
 Isomers; Functional group isomers
– Nomenclature (the rules for naming the molecules)
 Common & IUPAC
– Amides: (alkylalkylamide) N-alkylalkanamide
– Amines: (alkylalkylamine) N-alkylalkanamine
– Physical properties (basic/simple)
 pH; BP; Solubility; Flammability
– Acids ~ hydrogen bonding!
– Esters ~ no hydrogen bonding (a lot like ethers)
– Amides: lower pH; most are solids @ RT
– Amines: higher pH; most are liquids @ RT
– Occurrence and uses (common)
 Acids - metabolic intermediates & products; antimicrobials
 Esters - flavors/fragrances; pheromones; medications
– Phosphate esters
 Amides - Urea; barbiturates; polyamides & polyurethanes
 Amines - Biochemical; Alkaloids
– Preparation (what basic reactions produce the molecules)
 Acids - Oxidation of aldehydes; of alkyl benzene
 Esters - Esterification (C. acid + alcohol); condensation polymerization
 Amides - (amidification) Amine + C. Acid --> amide
 Amines - Rxn w/ alkyl halide (in base)
– Characteristic reactions of the molecules
 Acids - Neutralization; Esterification; acid salts (rxn w/ SB or SA)
 Esters - Ester Hydrolysis (in acid); Saponification (in base)
 Amides - Hydrolysis (acidic & basic); polymerization
 Amines - Protonation<==> Deprotonation

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